I have exactly the same problem
This is not a matter of waiting a few seconds for the light to come on, that's correct functioning. My new retina mbp requires wiggling the cable to get it to charge. Not every time, but probably half the time. Also, once it's charging, sometimes it will stop charging before it's complete (or even close to complete) and then I need to wiggle the connection again to get it to restart. Also, it's not the cable, it's the connection to the machine. To get it to charge, you have to rock the connector at the point where it connects to the machine. Also, I see the same behavior on an old power supply that has a magsafe-1-to-magsafe-2 adapter on it. And that supply always worked fine w/ my old mbp. The point is that it's the machine, not the power supply. I guess I'll need to bring it back. I wonder how many of them have this problem.